RE: [APML] ESO Tarantula CCD image

["Sean Walker" <swalker@SkyandTelescope.com>]

He shared the entire process of taking and calibrating this image with the
users on the SBIG list. very impressive. The details are wrong on the APOD
page. it is a proper LRGB image. He even offers up the raw images for anyone
to try thier hand at processing- at "only" half rez (4000x4000) it is still
too big for me to play with :-P

Sean Walker

-----Original Message-----
From: owner-astro-photo@seds.org [mailto:owner-astro-photo@seds.org]On
Behalf Of Andreas Roerig
Sent: Friday, June 14, 2002 5:28 AM
To: astro-photo@seds.org
Subject: AW: [APML] ESO Tarantula CCD image


Hi Jerry,

I don't know if Mischa Schirmer is reading this list. But I know that he
usualy knows what he is doing.
You can reach him under
mailto:mischa@MPA-Garching.MPG.DE

He is pro and amateur in one person.
A few days ago he explained the steps that he used to process this image
on the german CCD-list. Unfortunately I deleted that mail.

Regards
  Andreas


:=================================
: Andreas Roerig
: Bahnhofstr. 16
: 65599 Dornburg-Wilsenroth
: Tel. 06436/28137
: http://home.t-online.de/home/a.roerig/index.htm
: (Letzte Aktualisierung: 03.06.2002)



> -----Ursprüngliche Nachricht-----
> Von: owner-astro-photo@seds.org
> [mailto:owner-astro-photo@seds.org] Im Auftrag von Jerry Lodriguss
> Gesendet: Freitag, 14. Juni 2002 07:16
> An: astro-photo@seds.org
> Betreff: [APML] ESO Tarantula CCD image
>
>
> It appears the pros are using techniques developed by
> amateurs, which would
> be something to be proud of, but the pros are doing it incorrectly!
>
> Scroll down to the bottom of this page to the technical
> information about
> the photos:
>
http://www.eso.org/outreach/press-rel/pr-2002/phot-14-02.html

It says:

>is an LRGB composite image, using a processing technique known as
>"Luminance Layering". The red, green and blue images were stacked for
the
>Luminance (L) channel, yielding a black and white, high S/N-ratio
image.
>In order to show details in the bright centre of the nebula as well as
the
>much fainter outer filaments, a non-linear filtering technique known as

>"DDP" (cf. http://www.asahi-net.or.jp/~rt6k-okn/viewgrap.htm for more
>details) was applied to the Luminance image. In parallel, the three
colour
>channels were combined in the usual way into an RGB colour image. The
>colour information from the latter image was then copied onto the
>Luminance image.


Notice they are making the luminance layer out of a combination of the
red,
green and blue filtered images.

I wonder if they know they are not gaining anything by doing this
because
they did not shoot a separate high resolution luminance channel with a
higher signal to noise ratio to start with.

The signal to noise ratio from combining the RGB channels is the same if

it's color, or if it's black and white.

I'm not talking about applying Okano's DDP to the image.

Maybe someone should clue them in... <G>

Jerry

Astronomical photography: http://www.astropix.com

Sports Photography: http://www.astropix.com/SPORTSPIX/INDEX.HTM


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